diff --git a/durabletask/task.py b/durabletask/task.py
index 2650bfd..66abc28 100644
--- a/durabletask/task.py
+++ b/durabletask/task.py
@@ -322,6 +322,8 @@ def on_child_completed(self, task: Task[T]):
             # The order of the result MUST match the order of the tasks provided to the constructor.
             self._result = [task.get_result() for task in self._tasks]
             self._is_complete = True
+            if self._parent is not None:
+                self._parent.on_child_completed(self)
 
     def get_completed_tasks(self) -> int:
         return self._completed_tasks
@@ -423,6 +425,8 @@ def on_child_completed(self, task: Task):
         if not self.is_complete:
             self._is_complete = True
             self._result = task
+            if self._parent is not None:
+                self._parent.on_child_completed(self)
 
 
 def when_all(tasks: list[Task[T]]) -> WhenAllTask[T]:
diff --git a/tests/durabletask/test_task.py b/tests/durabletask/test_task.py
index 81cc8a2..d8ec88e 100644
--- a/tests/durabletask/test_task.py
+++ b/tests/durabletask/test_task.py
@@ -46,6 +46,51 @@ def test_when_all_happy_path_returns_ordered_results_and_completes_last():
     assert all_task.get_result() == ["one", "two", "three"]
 
 
+def test_when_all_is_composable_with_when_any():
+    c1 = task.CompletableTask()
+    c2 = task.CompletableTask()
+
+    any_task = task.when_any([c1, c2])
+    all_task = task.when_all([any_task])
+
+    assert not any_task.is_complete
+    assert not all_task.is_complete
+
+    c2.complete("two")
+
+    assert any_task.is_complete
+    assert all_task.is_complete
+    assert all_task.get_result() == [c2]
+
+
+def test_when_any_is_composable_with_when_all():
+    c1 = task.CompletableTask()
+    c2 = task.CompletableTask()
+    c3 = task.CompletableTask()
+
+    all_task1 = task.when_all([c1, c2])
+    all_task2 = task.when_all([c3])
+    any_task = task.when_any([all_task1, all_task2])
+
+    assert not any_task.is_complete
+    assert not all_task1.is_complete
+    assert not all_task2.is_complete
+
+    c1.complete("one")
+
+    assert not any_task.is_complete
+    assert not all_task1.is_complete
+    assert not all_task2.is_complete
+
+    c2.complete("two")
+
+    assert any_task.is_complete
+    assert all_task1.is_complete
+    assert not all_task2.is_complete
+
+    assert any_task.get_result() == all_task1
+
+
 def test_when_any_happy_path_returns_winner_task_and_completes_on_first():
     a = task.CompletableTask()
     b = task.CompletableTask()